Design and Construction of Infiltration Facilities

There are important aspects of the design and construction of all infiltration facilities (infiltration basins and trenches, rain gardens and swales) that need research and documentation. First, a pre-design tool is needed for a rapid assessment of sites to minimize risk of infiltration failure and prioritize suitable areas for infiltration. Second, a method is needed to measure infiltration capacities of any relatively shallow underground confining layers during the design phase. Though vital for infiltration facility design, there is currently no well-established protocol for performing these measurements. Third, the number of infiltration measurements required to design infiltration facilities of different sizes has never been established. Fourth, a rapid infiltration measurement device is required during construction to ensure that the facility, as constructed, will infiltrate water at the rate designed. Finally, a post-construction forensic analysis protocol is required to determine why an infiltration facility is infiltrating water too slow or too fast. The objectives of the proposed research will be to investigate, provide documentation, and develop implementation tools on these four items to be used by cities, counties and MnDOT in design and construction of infiltration facilities. The goal is to develop documented design standards that promote cost-effective design and assessment of infiltration facilities and produce infiltration facilities that will meet volume control requirements of watershed districts and municipalities throughout the State of Minnesota. Design standards will be submitted for inclusion in the Minnesota Stormwater Manual.